Owners manual

2: Configuring Modbus
Modbus Protocol User Guide 15
Character Timeout (10-7050 msec)
This sets the timeout between characters received. Official Modbus/RTU defines a
3.5 character time-out, but complex devices have various interrupts that can cause 5
to 10 character “pauses” during transmission. A safe value for general use with
Modbus is 50 msec.
Note: Setting this value lower than 50 msec will not improve performance
and may even make performance worse. The IAP Device Server uses an
intelligent length-predicting algorithm to detect end-of-message in
Modbus/RTU. This “character timeout” is only used with user-defined or non-
standard Modbus functions.
Message Timeout (200-65000 msec)
This sets the timeout for a response from a connected slave both serially and by
TCP/IP.***
Serial TX delay after RX (0-1275 msec) (0)
This feature inserts a delay between the Modbus/TCP master requests. The first
request is sent out of the serial port of the IAP Device Server to the Modbus slave.
When the slave’s response enters the serial port of the IAP Device Server, it triggers
this timer. After the specified delay is reached, the next master request is allowed to
pass through the serial port of the IAP Device Server, and the timer is reset. This
feature is particularly useful when using RS485 2-wired serial protocol. The delay
gives ample time for the RS485 slave devices to turn their transmitters off and their
receivers back on.
Swap 4x/0x to get 3x//x (1y)
This setting allows the MBF to convert “input” resistor data to “holding” resistor data.
It also converts coil and contact data. This feature is useful for Modicon I/O scanners.